Last night I went to put fuel in the 68, and after starting up easily and going about a block down the road, she started running really rough, like 1/4 throttle to keep it idling at less than 500 rpm. Limped back to the garage, hoping for a vacuum leak, or something obvious, didn't find anything. Eventually, I took off my brand new FBO ignition, and took the factory dizzy out, put in my $50 ebay HEI dizzy, ran perfect after I did that.
This is my second ignition box that I've had problems with, first a Mallory 690 box, now the FBO. I'm wondering if funky wiring in the car could be partially to blame. I'm running a squareback alternator, with one terminal grounded back to the case, and the voltage regulator that was on the car when I bough it. Is it possible that the charging system could be causing problems with the ignition system? My theory is that the nicer ignition boxes have tighter tolerances than the cheapo HEI, which is why the HEI works when the others don't.
